1. Field of the Invention
Embodiments of the present invention relate to a display panel applied to flat panel display devices, and particularly, to a plastic panel.
2. Discussion of the Related Art
Flat panel display (FPD) devices are applied to various electronic products such as portable phones, tablet personal computers (PCs), notebook computers, etc.
The FPD devices include liquid crystal display (LCD) devices, plasma display panels (PDPs), organic light emitting diode (OLED) display devices, etc. Recently, electrophoretic display (EPD) devices are widely used as the FPD devices.
FIG. 1 is a view schematically illustrating a configuration of a related art FPD device. FIG. 2 is a sectional view of an embodiment illustrating a state in which a display panel of FIG. 1 is adhered to a driving integrated circuit (IC) by a conductive member.
The FPD device, as illustrated in FIG. 1, includes a display panel 10 that displays an image, a printed circuit board (PCB, main board) 70 on which various circuit components are mounted, a flexible printed circuit (FPC) 60 that connects the PCB 70 to the display panel 10, and a driving IC (D-IC) 20 that is mounted on the display panel 10 and drives the display panel 10 according to an electrical signal transferred from the PCB 70 through the FPC 60.
The display panel 10 may use various types of panels, such as a liquid crystal panel, a PDP, an organic light emitting display panel, an EPD panel, etc., depending on the types of the above-described FPD devices. Generally, the display panel 10 is configured with an upper substrate 16 and a lower substrate 15.
The display panel 10 includes a display area that substantially displays an image, and a non-display area that cannot display an image. A plurality of output link lines 30, which electrically link the driving IC 20 to a plurality of panel lines (gate lines or data lines) disposed in the display area, and a plurality of input link lines 50 electrically linking the driving IC 20 to the FPC 60 are arranged in the non-display area.
The driving IC 20 may be a data driver IC for driving the data lines of the display panel 10, a gate driver IC for driving the gate lines of the display panel 10, or a display driver IC (DDI) for integratedly driving the data lines and the gate lines. In FIG. 1, the display driver IC is illustrated as an example of the driving IC 20.
In a chip-on glass (COG) type in which the driving IC 20 is directly mounted on the display panel 10, as illustrated in FIG. 1, when an anisotropic conductive member 40, such as an anisotropic conductive film (ACF), is disposed between the plurality of link lines 30 and 50 and the driving IC 20, by compressing the driving IC 20 to the display panel 10, the driving IC 20 is electrically connected to the link lines 30 and 50.
To this end, as illustrated in FIG. 2, a link terminal (bump) 21 is disposed at one side surface of the driving IC 20 corresponding to the link lines 30 and 50, and thus, when the driving IC 20 is compressed, a lower side surface of the link terminal 21 compresses a conductive ball 42 included in the conductive member 40 and is hardened, thereby electrically linking the link lines 30 and 50 to the driving IC 20. In this instance, a plurality of transparent electrodes 31 and 51 are formed on the link lines 30 and 50, for assisting electrical connections between the link terminal 21 and the link lines 30 and 50.
In this instance, a sufficient number of conductive balls are sufficiently compressed by the link terminal 21 to ensure electrical conductivity between the display panel 10 and the driving IC 20. Therefore, the above-described compression process necessarily needs an operation that tests whether a conductive ball 42 is sufficiently compressed by the link terminal 21.
To this end, a scheme is used in which a microscope is disposed under the display panel 10 so as to check fine indentations 32 and 52 formed on the transparent electrodes 31 and 51 or the link lines 30 and 50 through the display panel 10, and a camera captures images of the indentations 32 and 52 checked by the microscope to acquire image data, thereby testing the indentations 32 and 52 in which the link lines 30 and 50 or the transparent electrodes 31 and 51 are compressed by the dented conductive ball 42. Here, the indentations denote squashed marks that, when the conductive ball 42 is compressed on the link terminal 21 and the display panel 10, are formed on the transparent electrodes 31 and 51 or the link lines 30 and 50 by denting a portion of the conductive ball 42. That is, there being a number of marks squashed by the dented conductive ball (or broken conductive ball) 42 denotes the link lines 30 and 50 being closely adhered to the link terminal 21, and moreover denotes the link terminals 21 being electrically connected to the link lines 30 and 50.
Recently, the use of FPD devices using a plastic panel, which is not damaged even when being folded or rolled, continues to increase.
Especially, e-books which users can carry and use are manufactured with an EPD panel, in consideration of characteristics in which power consumption is low, the cost is low, and the e-book is accommodated and kept in a space with various articles placed therein like bags. The EPD panel is manufactured as a plastic panel.
In addition to the e-books, various electronic products are manufactured with the plastic panel for portability reasons. In addition to the EPD panels, liquid crystal panels, plasma display panels, organic light emitting display panels, etc., may be manufactured as the plastic panel.
Here, the plastic panel denotes a display panel in which a base substrate configuring the display panel 10 is formed of a synthetic resin such as plastic. That is, a base substrate of the plastic panel is a plastic base substrate.
Even when the driving IC 20 is mounted on the plastic panel 10, the above-described conductive ball 42 and compression process are used, and an operation of testing whether the conductive ball 42 included in the conductive member 40 is sufficiently compressed to the link terminal 21 is applied.
However, in the plastic panel 10, it is difficult to visually determine a degree of indentation in which the link lines 30 and 50 are compressed and dented.
Specifically, in the display panel 10 using a glass substrate as a base substrate, degrees of indentations shown through the link lines (metal layers) 30 and 50 or the transparent electrodes 31 and 51 are differently shown depending on a bonding condition between the conductive ball 42 and the link terminal 21, and a COG bonding condition and a degree of indentation are determined by comparing the degrees of indentations. However, in the plastic panel 10, since degrees of indentations based on the COG bonding condition are similar, it is difficult to check a difference between the degrees of indentations.
To provide an additional description, in the plastic panel 10, when the conductive ball 42 is compressed onto the link terminal 21 and the plastic base substrate, the conductive ball 42 is dented or broken and thus stuck into the plastic base substrate through the link lines 30 and 50 without being closely adhered to the link terminal 21 and the plastic base substrate, and thus, the number of dented conductive balls 42 is reduced. For this reason, it is difficult to determine a difference between degrees of indentations using the dented conductive ball 42. Particularly, since the link lines 30 and 50 are formed of opaque metal, in the plastic panel, it is more difficult to determine a degree of broken (a degree of dented) conductive ball 42.